Recording fixes: date folders on top, and multi-track honours the Source setting

Two issues Ed found testing:
 * The default recordings path was recordings\<machine>\, so date folders nested under a
   machine-name folder. Dropped the per-machine subfolder — recordings now nest by date at the
   top (recordings\<yyyy-MM-dd>\...); the machine name still appears in split-track file names.
 * Multi-track always created the "me" (sent) track regardless of the Source setting, so a
   receive-only recording wrongly produced a track of your own machine. Multi-track now follows
   Source like single-file does: peer (received) tracks unless "sent only", and your own (sent)
   track only when Source is "both" or "sent only".

Held for next release.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/RemSound.App/RecordingController.cs

@@ -154,8 +154,14 @@ internal sealed class RecordingController
         var ext = AudioRecorder.ExtensionFor(s.FileFormat);
         var time = now.ToString("HH-mm-ss");
 
+        // Multi-track follows the Source setting like single-file recording does: peer (received)
+        // tracks unless "sent only", and your own (sent) track only when you're actually recording
+        // your send ("both" or "sent only") — so a receive-only recording no longer makes a "me" file.
+
         // One track per connected peer (their received audio only), created up front on the UI thread
         // so the audio-thread tap never has to open a file. Peers that join mid-recording aren't added.
+        if (s.Source != RecordingSource.SentOnly)
+        {
             var recs = new Dictionary<string, PeerTrack>();
             var usedNames = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
             var byAddr = new Dictionary<string, string>();
@@ -171,13 +177,17 @@ internal sealed class RecordingController
             peerTracks = recs;
             receiver.SetPeerRecordTap(OnPeerRecordBlock, raw: s.BypassShaping);
             receiver.OnRecordBlockComplete = FlushPeerTracks;
+        }
 
         // Your own track — your sent audio.
+        if (s.Source != RecordingSource.ReceivedOnly)
+        {
             var mePath = Path.Combine(folder, $"{Sanitize(Environment.MachineName)} {time}.{ext}");
             meRecorder = new AudioRecorder(WithSource(s, RecordingSource.SentOnly), diagnostic, OnRecorderFinished, mePath);
             sender.OnSentSamples = meRecorder.WriteSent;
+        }
 
-        diagnostic($"recording: started multi-track → {folder} ({recs.Count} peer track(s), format={s.FileFormat}, bypass={s.BypassShaping})");
+        diagnostic($"recording: started multi-track → {folder} ({(peerTracks?.Count ?? 0)} peer track(s){(meRecorder is not null ? " + your send" : "")}, source={s.Source}, format={s.FileFormat}, bypass={s.BypassShaping})");
     }
 
     // Audio thread. Route each peer's block to that peer's recorder. peerRecorders is fully built at

src/RemSound.Core/RecordingTypes.cs

@@ -127,11 +127,10 @@ public sealed class RecordingSettings
 
     /// <summary>Default folder path used when <see cref="Folder"/> is blank. Computed at
     /// call time (not cached) so a launch from a different exe directory picks up that
-    /// directory rather than the first-load one. The per-machine subfolder lets two
+    /// directory rather than the first-load one. Recordings nest by DATE inside this — the
-    /// machines sharing a Dropbox-backed RemSound install keep their recordings tidily
+    /// machine name lives in the split-track file names, not a top-level folder.</summary>
-    /// separated by sender identity.</summary>
     public static string DefaultFolder() =>
-        Path.Combine(AppContext.BaseDirectory, "recordings", Environment.MachineName);
+        Path.Combine(AppContext.BaseDirectory, "recordings");
 
     /// <summary>Returns the resolved folder this profile would record into right now —
     /// either the explicit <see cref="Folder"/> if set, or <see cref="DefaultFolder"/>.